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Warping 101 In Ableton Live

Live looks at the length of an audio file and the current song tempo to guess how many bars long a loop is.

It's back to basics for this month's Live workshop, with an overview of Live 's time-warping technology.

The subject of warping has come up in various contexts in our regular Live workshops, but we've yet to offer a straightforward beginners' guide to the unique way in which Live handles audio. When you're new to Live, especially if you're used to how traditional sequencers and recording packages work, it can be quite difficult to figure out exactly what is happening (at least, it was for me!).

If Live thinks your loop is half or double its correct tempo, you can correct it in the Clip view.When importing an unedited audio file, you will have to set up the loop start and end points manually.Here, the bar one and loop start points have been moved to the downbeat of the audio Clip.Firstly, I should say that you can choose to treat Live like a normal audio recorder by switching off all warping. This can be done globally in Preferences by switching Loop/Warp Short Samples to 'Unwarped One Shot', and Auto-Warp Long Samples to 'Off'. You can now freely record and drag audio into the Arrangement, and the audio will be played back at its original speed, ignoring the tempo of the Live song. However, one of the central purposes of Live is to try to conform disparate audio sources to the tempo of the Live project. This also means that you can change the overall tempo, or draw a changing tempo graph, and the audio will stay in sync. So how exactly is Live treating audio that you add to the project? How does it know the tempo of the audio you drag in?

One of the sources of confusion is that there are really three different ways in which time-warping comes into play in Live. The first is when importing audio loops, or 'Clips'; the second is when you import longer passages of music; and the last is when you adjust the internal timing of a Clip manually. When you import an audio file into Live, the program has to make a fairly complicated assessment of the nature of the audio, and decide what it should do with it. The first decision it makes is whether the audio file is a short section of music that should be looped, or a longer section, such as an entire track, which should be sync'd along the timeline.

The decision Live makes is based on both the length of the audio file, and the current tempo of the session. Let's take an example. I created a project, set the tempo to 125 bpm, and dragged a loop from my loop library into the Arrangement (as shown in the screen at the top of this page). Based on the length of the sample, Live guessed that this was a four-bar loop with respect to the song tempo. In this case, the guess was spot-on, as the audio file was indeed a correctly edited four-bar loop, and was at the close tempo of 132bpm. I then dragged another audio file into track two (as in the screen on the left), this time of the same four-bar drum pattern recorded at 65bpm, so the sample is twice as long in real time. This time, Live makes the incorrect assumption that the loop's tempo is close to the song's tempo, and decides that it's an eight-bar loop at 130bpm.

There are a couple of ways to respond to this. The bottom of the screen shows the Clip view for the 65bpm loop. The field labelled 'Seg. bpm' displays the original bpm speed that Live has assumed the loop to be at. In this case, it has guessed double the actual tempo. The two buttons below, labelled ':2' and '*2', let you halve or double this manually (you can also type a value in). If I change the tempo here to 65bpm, the loop will be correctly re-assessed as being four bars long. However, the factor to take into consideration is that Live will now try to warp the sample to play it back at the song tempo of 125bpm. As this is nearly double the sample's native speed, it's likely to sound weird and time-compressed. In this situation, leaving the incorrect tempo assessment means that the loop will play back at close to its original tempo.

Looking again at the Clip view in the screen shot on the previous page, you will see that there are bars and beats labelled along the top of the waveform, with the first and last positions highlighted in yellow. These yellow points are called Warp Markers. When you import or record a loop into Live, it adds Warp Markers to the beginning and end of the Clip. These markers are Live 's guide to how to stretch or compress Clips. The markers always line up with points on the timeline, and between the markers Live speeds up or slows down the Clip with respect to its original tempo, in order to keep the markers aligned with the master tempo track. In our example, bar one of the loop is exactly at the beginning of the audio file, so the Warp Markers line up correctly and the loop plays back in time. However, this won't be the case if you drag in a Clip that hasn't been pre-edited into a perfect loop.

By manually setting bar and loop markers, you can create new loops from any audio on your hard drive.Auto-Warp often needs some help determining where bar one should be.After locating the first bar, you can tell Live to automatically detect the tempo for the rest of the recording.Learning how to manipulate the Warp and Loop properties means that you can free yourself from using only pre-cut loops. Here's an example: in the screen at the top, I've dragged in a short recording of an analogue synth sequence from a Pro Tools session. As usual, Live has made a guess about the length and tempo of the Clip, assuming it's a pre-prepared loop. We can ignore this and make the settings manually. You can see that there's a period of silence at the start of the Clip, and listening to the loop, I can also hear that the downbeat of the loop actually starts on the second peak of the waveform. In the screen below, I've moved the bar one Warp Marker and aligned it with this peak. Above the first Warp Marker are two arrows. The top one represents the loop start position, and the lower one is the playback (launch) start position.

Hitting Play, the Clip starts on the beat, but goes out of sync because the tempo settings are wrong, which is what you'd expect at this stage. In this example, I've decided that I want to use the first four bars of the recording as a loop. Listening to the loop and counting out the four bars, I identify the point in the waveform where my loop should end. I now need to tell Live that this point is the downbeat of bar five. Double-clicking the bar five label in the ruler turns bar five into a Warp Marker. By dragging this marker left or right, I can set which point in the waveform is 'pinned' to bar five. In this example, I need to drag it to the right, effectively speeding up the tempo of the Clip between bars one and five. The end marker is still in place, so everything after the bar five marker has to be slowed down to meet the subsequent time points. The final step is to change the loop length to four bars. This can either be done by altering the loop-length number field or by dragging the loop-end marker above the waveform to the bar five position. The bottom screen shows the finished loop, with the correct original tempo of the recording displayed.

When Live guesses that a sample you are importing is over 16 bars long, it determines that it's not a loop at all, but a long recording or an entire song. It then analyses the audio using a beat-detection algorithm, and tries to add beat markers to sync the tempo with the current Live song's tempo track. This happens with varying degrees of success, from pretty good to nowhere near! You usually need to make some manual refinements to auto-warped audio. Let's consider a simple example first: a techno track that starts with a four-on-the-floor kick. After dragging the Clip in, you have to wait a few moments while the 'Sample Analysis in Progress' message appears in the waveform display. When it finishes, you will see the results of the analysis as Warp Markers in the waveform. For electronic music with no tempo changes, as in our example, this may be just one Warp Marker (on bar one) and the detected tempo. Acoustic music will generate many Warp Markers representing tempo changes and subtle variations in timing.

Playing back the track against Live 's metronome reveals that the analysis has been largely successful, although the track is playing slightly off the beat. This is very common: for some reason the bar one marker is rarely placed correctly. Zooming in reveals that the marker is slightly late (although it's just as often early). As there are no other markers, you can simply move it by hand and the whole grid will be realigned correctly.

This recording has been correctly analysed; the yellow Warp Markers indicate subtle tempo changes.This four bar bass line has been recorded intoLive, and now needs some help with timing.Part of the bass line before and after timing correction. The bar and beat markers have been warped so that notes fall on the grid. A rock track recorded with no click presents a tougher challenge. In the next example I imported a track of this kind and the analysis failed to identify bar one correctly. This time, realigning the grid won't work, because there are many Warp Markers throughout the track, charting the drifts in tempo. The solution is to identify bar one, then tell Live to redo its auto-warping based on this starting point. This is done by placing the bar one marker correctly, then right- or Ctrl-clicking it and choosing the 'Warp from here' command. In this example, the result was a correctly sync'd track throughout. You can see the process in the top three screens to the right. If you do need to re-align the grid slightly (maybe the downbeats are all a bit early) you can select all the Warp Markers by choosing Edit / Select All, and move them all together.

Warp Markers can also be used to tighten up timing. Say I've recorded a four-bar bass line, but the performance is a bit loose. This is where Live really comes into its own, as doing the following operations in other packages would mean cutting up the audio. In Live, you can move Warp Markers so that musical events occur on the desired beat (or sub-beat), and all audio in between is subtly time-stretched to maintain smooth playback.

The first step is to 'anchor' the end of the loop, by double-clicking the bar five marker. You can zoom in and work through the waveform, seeing which notes are off the grid. Unless you've played really badly, you should be able to see where each note was supposed to be. To pull a dodgy note back into time, double-click the number above the nearest grid and move it into line with the note in the waveform — but there's one thing you need to do first. In order to stop the neighbouring notes from being pulled out of time when you move the grid, you need to set anchors. Anchors are created by setting Warp Markers at the grid positions of the notes that are adjacent to the one you are moving. As you can see in the top part of the screen at the bottom of this page, the middle note is clearly out of time. In the second screen, the neighbouring notes have been anchored, and the grid has been warped to pull the note into time.

Obviously, as well as tightening audio performances to the grid, you can use Warp Markers to actually mess about with the timing and groove of recordings. Live 6 also makes it easy to apply the same warping to multiple Clips at the same time, a subject that we'll return to in a future Live technique feature.